This invention pertains to valve mechanisms, and particularly to pinch valves.
Although pinch valves have generally been known as a relatively inexpensive type of valve mechanism, pinch valves are primarily used only for a few rather select purposes. Unfortunately, prior art pinch valves do not lend themselves to many practical applications.
As shown in FIG. 1, a typical pinch valve comprises an elastic tube (comprised of rubber or plastic, for example) which forms a passage for the flow of fluid therethrough and a choking device which shuts the passage of fluid in the elastic tube when the tube is compressed.
FIG. 2 shows an enlarged section of a bending corner portion 2 occuring at one side of a compressed tube. At the inner surface of the bending corner 2 a small hollow 1 still remains. The hollow 1 permits an undesirable leakage of fluid through the tube. It is difficult to totally eliminate the small hollows 1 which occur on both sides of the tube. In this respect, if a very large stress is applied to the elastic tube in an attempt to eliminate the hollows, permanent distortions or cracks may occur at the bending corners 2 or 3 of the elastic tube and may impair the endurance of the pinch valve.
In view of the above, pinch valves have been conventionally used primarily in connection with low pressure fluids under conditions in which some leakage of fluid is tolerable. Some prior art pinch valves, however, have been fabricated to include an elastic tube having a cross-section of special shape. Although pinch valves of this type are durable and have less leakage, such valves require a very thick elastic tube and a strong force to compress the tube and shut the passage.
Therefore an object of this invention is to provide a pinch valve which has high sealing performance.
An advantage of the invention is to provide an inexpensive pinch valve which can be fully operated by a small pressing force.
Another advantage of the invention is to provide a pinch valve which has a broad range of applications.